In optical semiconductor devices heretofore in use, the optical semiconductor elements are encapsulated in a transparent thermosetting synthetic resin such as, e.g., an epoxy resin so as to prevent deterioration. However, there has been a problem that these synthetic resins upon curing impose a stress on the optical semiconductor elements to cause deterioration.
For preventing such stress imposed on optical semiconductor elements, an optical semiconductor device has been reported which includes an optical semiconductor element directly sealed with a thermosetting synthetic resin reduced in stress imposition and further with a transparent thermosetting synthetic resin (see, for example, patent document 1).
Patent Document 1: JP 2003-179267 A.
However, the optical semiconductor device described above is ineffective in relieving the stress caused by a difference in the coefficient of linear expansion between the encapsulating resins and the wiring circuit board, although the stress to be imposed on the optical semiconductor element may be relieved. There are hence cases where this optical semiconductor device warps. Warpage not only causes the optical semiconductor device to have a shape failure but also results in cases where the quantity of light emitted from the light emission-side face becomes uneven. Such problems are important especially for the backlights of liquid-crystal displays in which a reduction in thickness is desired.